So recently I switched Windows from XP to Win7 ×64 and all of a sudden I can't convert videos to be played on Philips3360 and Sony divx players. When ever I put USB stick in it to play the video I get the message "Video Codec not supported" and I use the same program like before to convert the "Format Factory" and I tried almost every combination. I just don't get what's the sudden difference and what should I do?

Yes, many fourcc codes are used to indicate MPEG 4 Part 2, XVID, DIVX, DX50, MP42, etc. Not all players accept all of them. And some players are case sensitive. And the container matters too. See "Codec ID" and "Codec ID Hint" in MediaInfo.